Field of the Invention
The present invention relates to a range switching apparatus including what is called a shift-by-wire system in which a driver selects a shift range, for example, by shift lever, that is set by an electric signal.
Description of the Related Art
This application is related to copending U.S. application Ser. No. 14/449,815, filed Aug. 1, 2014, commonly assigned with the present invention.
For example, as described in Patent Document 1 (the copending application), a range switching apparatus including a motor, a speed reduction mechanism and an output shaft within a shell member is known.
In the range switching apparatus described in the Patent Document 1, an electronic control unit is placed within the shell member, and a projected connector is provided on the housing body of the range switching apparatus, then a connector receiving a wire from an external unit is coupled to the connector of the housing body, thus the range switching apparatus is electrically connected to the external unit.
[Patent Document 1] U.S. Ser. No. 14/449,815 (JP-A-2014-78410)
However, the range switching apparatus described in the Patent Document 1 uses a sector-shaped external gear in a parallel shaft gear speed reduction part of the final stage of a speed reduction unit, which causes the distance between the gear shafts to increase, causing a problem of increasing the size of the range switching apparatus.
Further, the transmission side of a range switching mechanism includes a detent mechanism using a detent plate, a detent spring and the like so that fixedly positioning to individual shift ranges can be done, and also the transmission side of the range switching mechanism includes an inhibitor switch having the functions of recognizing a positioned range and turning on a positioning lamp corresponding to the individual positioned range, turning ON/OFF a power supply for other actuators, and the like. In addition to the detent mechanism and the inhibitor switch, the range switching apparatus is included, which also causes a problem of increasing the size of the overall range switching mechanism.
Further, in positioning to the individual shift ranges using the range switching apparatus, when a reverse starting torque from the output shaft of the range switching apparatus is equal to or less than a detent torque provided in the transmission, positioning to the individual shift ranges can rely on the detent torque, which facilitates positioning control of the range switching apparatus. However, in order to generate a torque needed for shift range switching by the range switching apparatus, a torque generated by a motor needs to be amplified using a speed reduction mechanism such as a gear.
However, in return for that, a reverse starting torque caused by a motor cogging torque of the range switching apparatus and a loss torque of the speed reduction mechanism increases, so this reverse starting torque exceeds the detent torque, resulting in difficulty in the control relying on the detent torque, which causes a problem of requiring high precision in controlling the range switching apparatus.